With the development of various industries, there is the possibility for an increase in a demand for an on-site or on-board miniature hydrogen manufacturing apparatus. A commercialized large-scale hydrogen manufacturing process is shown in FIG. That is, hydrocarbons are converted to synthetic gases containing hydrogen and carbon monoxide in a reformer 10, and water gas shift (WGS) is carried out in a carbon monoxide water gas shift reactor 20, and then, carbon monoxide is removed from the reformed gas in a hydrogen separator 30 using a catalyst or a separation membrane to generate hydrogen. In this regard, as heat of reaction (‘reaction heat’) needed in the reformer 10, heat of combustion (‘combustion heat’) generated by burning a part of hydrogen generated from the hydrogen separator 30 in a combustor 40 is used.
The hydrogen formation reaction using hydrocarbon can be preceded in many ways as shown reaction formulas of 1 to 3.CH4+H2O→CO+3H2, reaction heat: +206 kJ/mol  [Reaction Formula 1]CO2+CH4→200+2H2, reaction heat: +247 kJ/mol  [Reaction Formula 2]CH4+½O2→CO+2H2, reaction heat: −36 kJ/mol  [Reaction Formula 3]
Of these formulas, steam reforming according to reaction formula 1, wherein the concentration of hydrogen in the products is the highest, is attracting attention.
A difficulty in this process is that supplying heat necessary for the reaction is crucial, as shown in reaction formula 1. Because it is possible to obtain 95% or more for the conversion rate of hydrocarbon (methane) at 750□ or higher in the case of steam reforming, a great deal of effort is needed to supply reaction heat and maintain a high temperature.
The reaction heat necessary for the above reaction formula 1 is generated through combustion (catalytic oxidation or combustion) of hydrocarbon as in reaction formula 4.CH4+2O2→CO2+2H2O, reaction heat: −801 kJ/mol  [Reaction Formula 4]
In order to make heat transfer effectively in the process of reaction formula 4, it is necessary to have a material having a high temperature difference (ΔT), a wide contact area (A), and a high heat transfer coefficient (k).
However, it is impossible to indefinitely raise a temperature of flame necessary for heating in order to obtain a desired temperature difference, and there is a problem of component materials, and also there is limitation in that the component materials have inherent heat transfer coefficients which are determined independently.
Therefore, the key controllable factor in the construction of the reactor is concluded to be the enlargement of the heat transfer area (A).
As a reactor for such a purpose as described above, there is an attempt to make use of a reactor having micro-channels on a thin metal plate. In particular, the present applicant has developed apparatuses in Korean Patent Registration No. 10-0719486 (Micro-combustion/reforming reactor) and Korean Patent Application No. 10-2009-0124091 (Hydrocarbon reforming apparatus using a micro-channel heater). The above patents disclose an invention in regard to a micro-combustion/reforming reactor with a specific module configuration, wherein a wide contact area per unit volume can be secured by laminating a plurality of processed thin metal plates in multilayer structure.
A combustion reaction of hydrocarbon (NG, LPG and alcohols) necessary for generation of reaction heat is an intensive reaction that generates a considerably high heat value, and can be carried out through either catalytic combustion or non-catalytic combustion.
The above catalytic oxidation has problems in that the catalytic bed should be preheated up to a specific temperature zone in which an oxidation reaction can proceed, and durability should be considered when exposed for a long time during coating the inside of the micro-channel. That is, it is difficult to maintain the oxidation activity of an oxidation catalyst when the oxidation catalyst is exposed to high heat throughout operation of a combustion apparatus, therefore, this difficulty acts as a limitation in putting this system to practical use. Further, since the non-catalytic combustion requires a space for an expanding ignition flame, it cannot be applied to a compact micro-channel reactor.
Various forms of hydrocarbon reforming catalyst have been put to practical use, and methods of coating a catalytic agent are disclosed in many patents and documents. However, in order to use the hydrocarbon reforming catalyst in a micro-channel reactor as in the present invention, a reactor must be constructed to be compatible with characteristics of the catalyst.
In particular, since the micro-channel reactor is used in a small space, an area in which the reformed gas can reliably contact is preferably widened as much as possible in a limited space, in order to obtain a maximum reforming efficiency. Accordingly, there is still a need for a solution to overcome the foregoing problem.